Chapter 4 Introduction

Morgan Kaufmann Publishers 31 January 2013ALU ControlALU used forn Load/Store: F = addn Branch: F = subtractn R-type: F depends on funct fieldALU controlFunction0000 AND0001 OR0010 add0110 subtract0111 set-on-less-than1100 NOR§4.4 A Simple Implementation SchemeCSE 420 Chapter 4 — The Processor — 21ALU ControlAssume 2-bit ALUOp derived from opcoden Combinational logic derives ALU controlopcode ALUOp Operation funct ALU function ALU controllw 00 load word XXXXXX add 0010sw 00 store word XXXXXX add 0010beq 01 branch equal XXXXXX subtract 0110R-type 10 add 100000 add 0010subtract 100010 subtract 0110AND 100100 AND 0000OR 100101 OR 0001set-on-less-than 101010 set-on-less-than 0111CSE 420 Chapter 4 — The Processor — 22